Tomljanović played her first professional ITF Circuit event in October 2008 in Mexico City, and lost to Estefanía Craciún in the semifinals. She then qualified for another ITF event in Mexico City, but lost to Karolina Kosińska in the second round. In January 2009, she qualified for the ITF event in Boca Raton, Florida, where she lost to Heidi El Tabakh in the second round. Tomljanović was awarded a wild card for 2009 BNP Paribas Open in Indian Wells, and lost to Angela Haynes. Tomljanović then made a chain of three consecutive losses in the second rounds, at the ITF tournaments in Redding, California, Osprey, Florida, and Makarska, Croatia, losing to, respectively Rika Fujiwara, Kateřina Kramperová and Ana Savić. At the ITF event in Zagreb, she lost to Tereza Hladíková in the first round. On 10 May 2009 in Zagreb, Tomljanović won her first ITF doubles title, partnering with Croatian fellow Petra Martić. Tomljanović missed most of 2012 due to mononucleosis.